1. Field of the Invention
The present invention relates to a distance-measuring optical apparatus for measuring a distance to an object to be imaged using an imaging optical system and an image sensor, a distance-measuring method using such a distance-measuring optical apparatus, and a distance-measuring system for generating information to be recognized by the operator in accordance with the distance measured by the distance-measuring optical apparatus and presenting the information. The present invention also relates to an in-vehicle imager including the above-described distance-measuring optical apparatus, and an in-vehicle driving support apparatus including the above-described distance-measuring system.
2. Description of the Background Art
As distance-measuring optical apparatuses for measuring a distance to an object to be imaged, apparatuses using a so-called triangular distance-measuring system are known. According to a triangular distance-measuring system described in, for example, Japanese Laid-Open Patent Publication No. 8-233571, light from a light emitting diode or the like is spot-projected toward a measurement target, the distance to which is to be measured, via a projection lens; and the light reflected by the measurement target is received by a position detection element via a light receiving lens. Based on the light receiving position detected by the position detection element, the distance to the measurement target can be found out.
Japanese Laid-Open Patent Publication No. 60-216206 proposes a three-dimensional image generation apparatus including an imaging section. The three-dimensional image generation apparatus described in Japanese Laid-Open Patent Publication No. 60-216206 includes an imaging section and a moving mechanism for moving the imaging section substantially perpendicular to an optical axis. Each time a three-dimensional image is to be taken, the imaging section is moved to take a plurality of images, and parallax is found by a operation based on the images, so as to generate a three-dimensional image.
According to the triangular distance-measuring system described in Japanese Laid-Open Patent Publication No. 8-233571, various elements for distance measurement are required including an optical source and an optical system for projecting light, a position detection element for receiving light, and the like.
In order to check the view behind a vehicle, an in-vehicle imager is occasionally mounted. In this case, it is necessary to measure a distance between the vehicle and an object behind the vehicle so as to grasp the distance accurately, in addition to visually observe the object. When using the triangular distance-measuring optical apparatus described in Japanese Laid-Open Patent Publication No. 8-233571 to measure the distance, an optical system for taking images and also an optical system for measuring distances are required. This enlarges the overall size of the apparatus against the general demand for size reduction.
The three-dimensional image generation apparatus described in Japanese Laid-Open Patent Publication No. 60-216206 is intended to generate a three-dimensional image when the imaging section is in a still state. This three-dimensional image generation apparatus is not intended to be used in a distance-measuring optical apparatus mounted on an in-vehicle imager for measuring distances at high speed in a moving body and outputting the distance-measuring results successively.